Filtration is one of the separation means commonly used in the laboratory to separate the solid particles out of the solid-liquid mixture. When the solid-liquid mixture is brought in contact with a filter media surface, the liquid passes through the filter media, but the solid material retains on the filter. Vacuum filtration is one of the rapid filtration methods commonly used in laboratory. The vacuum filtration involves a vacuum suction to cause pressure gradient which draws the fluid through the filter media such as filter paper, allowing for higher filtration rates and faster filtering than gravity filtration. The vacuum filtration devices usually consist of a filtration funnel, a side-arm connecting to a vacuum source, and a receiving receptacle. Sometimes, an adaptor may be needed to connect the filtration funnel and the receiving receptacle.
Buchner funnels as commonly used vacuum filtration devices are widely used. Some Buchner funnels come with side-arm connecting to the vacuum source, some do not. Buchner funnel without side-arm usually requires the use of neoprene or silicone rubber seal or frit to connect the receiving receptacle, such as flasks. In the operation of the vacuum filtration, the wear debris generated from the rubber seal can enter into the receiving receptacle, causing serious contaminations to the filtered fluid sample. After continued use, the rubber seals gradually wear or dry out, eventually leading to an air leak into the filtration system and resultant reduction in the vacuum filtration speed and effectiveness.
Buchner funnels are mainly made of porcelain and glass. It is very difficult to clean the perforated plate and/or filter media of Buchner funnels due to the clogging or obstruction by solid materials. The clogging solid materials may eventually enter into the receiving receptacle, easily contaminating the filtered samples. The clogging solid materials, such as catalyst particles, may also directly or indirectly react with the filtered samples, significantly impacting the purity and/or quality of the filtered samples. Sometimes the solid materials are the target product to be collected in some filtrations. For example, the precipitated solid materials are usually the target product to be collected in the material synthesis. In the application of the Buchner funnels with fritted filter discs made of borosilicate, quartz, or other porous materials, the pores of the filter media become easily clogged up by solid materials. The fritted filter disc must be thoroughly washed with a variety of solvents in multi-steps and unclogged prior to reuse. For example, to remove aluminous and siliceous residues inside the clogged pores, a recommended cleaning solution is 2% hydrofluoric acid followed by concentrated sulfuric acid; rinse immediately with distilled water followed by a few milliliters of acetone, and repeat the rinsing until all traces of acid are removed. To avoid irritating and corrosive hydrofluoric acid and concentrated sulfuric acid spills and burns, eye protection and chemically resistant gloves should be used when washing the Buchner funnels with fritted discs. An apron and fume hood may also be required depending on the cleaning solutions being used. Meanwhile, the use of significant amount of water and cleaning solvent will increase the filtration cost and effort.
Both 100 mL round bottom flask and 100 mL flat bottom flask with 24/40 standard taper joints are two types of the most commonly used flasks in the chemistry laboratory. The flask body depths (the distance from the bottom of the outer ground joint to the bottom of the flask) of above two types of flasks are both about 80 mm. The flask body depth may vary with the flask volume to some extent. For example, the flask body depths of, another commonly used, 250 mL short neck round bottom flask and flat bottom flask with 24/40 standard taper joint are about 100 mm and 95 mm, respectively. Similarly, the flask body depths of, further another commonly used, 50 mL round bottom flask and flat bottom flask with 24/40 standard taper joint are both about 58 mm. As compared to above flasks, 1000 mL round bottom flask and flat bottom flask with 24/40 standard taper joint are relatively not commonly used and their flask body depths are about 149 mm and 145 mm, respectively.
Currently, all the filtration funnels or Buchner funnels with side-arms are made of glass and have short outlet stems. The outlet tip of the short stem is not far away from the side-arm close to the vacuum source, and also barely or slightly protrudes the bottom of the connection joint. Therefore, as compared to the body depths of above commonly used 250 mL, 100 mL, and 125 mL flasks, the outlet tip the short stem of the Buchner funnels is observably in the upper part of receiving flask. In filtration operation, sometimes the liquid or filtered fluid is the target product to be collected. The existing design of the short outlet stem and the location of the outlet tip close to the side-arm connecting to the vacuum source will significantly increase the loss of volatile samples under vacuum filtration and the loss of filtered fluid samples sucked into the vacuum source. In some cases involving large loss of filtered samples under vacuum filtration, it may be necessary to make the unfiltered sample several times and filter several times to collect a sufficient quantity of the target product. Loss of the sample affects the product yield, directly increasing research and development time, cost, manpower, and subsequent commercialization process design, timing and profitability. The design of short stem outlet can cause splashing and foaming of the filtered fluid in the receiving receptacle. Splashing and foaming can cause the filtered fluid sample change in the components or promote chemical reactions between substances. For example, splashing of the high temperature filtered fluid to the wall of the receiving receptacle can cause solid crystals precipitating from fluid or solution. Splashing and foaming can damage the components of the filtered samples, such as the structure of macromolecules, i.e. cells or proteins. Buchner funnels have been widely used; however, there is a lack of disposable filtration funnel with reasonably long outlet stem, a further lack of disposable filtration funnel with side-arm for vacuum connection and reasonably long outlet stem.
In some filtration operation, the filter paper and filter media are directly placed by a hand into a vacuum filtration funnel, the solid particles in the solid-liquid sample can flow or leak from the gap between the outer edge of the filter media and the inner bottom plate or the inner sidewall of the filtration funnel to the receiving receptacle, causing the particle leakages and the resultant failure of the effective filtration and separation. In addition, an increase in the thickness of filter cake dramatically accelerates the blockage and obstruction. The smaller the pore size of the filter membranes and frits, the more pores are clogged. When the pores are partially and severely clogged, the filter membrane or filter frits and the receiving receptacle are exposed to strong vacuum conditions. Under strong vacuum conditions, the filter paper and thin filter membrane, even sealed to the bottom of the filtration funnel, can break or crack at the seal, causing the particles and unfiltered sample sucked into the receiving receptacle and severely impacting the filtration and separation. U.S. Pat. No. 4,702,834 discloses a filter membrane welded to the inner bottom of the filtration funnel with a weld width of 2.29 mm. U.S. Pat. No. 7,011,755 discloses a funnel with a final filter and integral prefilter which have one or more layers of prefilter material. The final filter at the bottom is sealed to the funnel; however, all the prefilters contact the funnel with non-absolute or releasable seal rings, allowing the passage of unfiltered sample. In forgoing patents, the filter frits or membranes are sealed only to the inner bottom of the funnel, forming a single seal. The seal width is narrow and there is no protective seal. Practically, the sealing joints in the strong vacuum condition may crack, resulting in the unfiltered sample sucked to the receiving vessel. In some filtration operation, a proper mixing of the sample mixture in the funnel is necessary to improve filtration effectiveness and reduce the filtration time. The long stirring rods made of glass and plastic sometimes directly contact and inevitably damage the seal welded joints, eventually leading to the unfiltered sample sucked into the receiving receptacle. In addition, above filter frits or membranes and the funnel sometimes are made of different materials showing different melting properties, which are very difficult to form the leak-free seal, and only sealed to the inner bottom of the funnel without a protective seal. A slight crack on the seal welded joints can cause the unfiltered samples sucked into the receiving receptacle. U.S. Patent Application 20100038303 and Chinese Patent Application 2010800640629 disclose a disposable polymer-structured filtering kit, but the lack of a welded integration between the filter frit and the filtration funnel will cause the leakage of unfiltered sample under vacuum conditions.
Many of Buchner funnels used in the laboratory are in fact made of glass individually by hand, suggesting a high labor cost, relative high pricing, and easily-broken feature of all the glassware. Some large Buchner funnels are made of ceramic, relatively bulky and heavy, and inconvenient to move during use. A few user-convenient filtration funnels have been developed, such as combined plastic Buchner funnels from SIGMA in the United States. However, all these funnels have no side-arms for connection to the vacuum source, need rubber gasket to seal, and not convenient to use. U.S. Patent Application 20100038303 and Chinese Patent Application 2010800640629 disclosures a filtration funnel which needs to connect with an external glass-made side-arm in application and not convenient.
In a summary, all these prior art techniques have the forgoing drawbacks. In the practical filtration, the solid materials as filter cake are target product to be collected, and sometimes the filtered fluid as filtrate to be collected, and sometimes both solid materials and filtered fluid to be collected. Therefore, there is a practical need for the object of the present invention to provide a cost-effective disposable vacuum filtration funnel to reduce or eliminate the loss of filtrate and filter cake, avoid contamination, and reduce filtration costs and time.